REUTERS/Toby MelvilleBritain's Queen Elizabeth and Prince Philip attend Trooping the Colour in London, Britain, June 17, 2017.
The Duke was at the Queen's side on Tuesday for the opening day of Royal Ascot and a source said he was on "good form" during the event.
The queen, 91, maintained her official schedule Wednesday, giving a speech outlining the government's legislative plan in Parliament, and attending the Royal Ascot horse races in the afternoon as had always been planned.
The queen outlined the government's legislative agenda in her speech Wednesday.
The Duke is the husband of Queen Elizabeth II.
The hospital admission was understood be a precautionary measure a rather than an emergency. Should she have skipped Royal Ascot while Philip is in hospital?
Buckingham Palace said there were no current plans for Philip to miss other royal engagements later this month.
He drinks moderately, takes the stairs and says he still fits into the uniform he wore on the day he married the Queen, nearly 70 years ago. It followed a hospitalization in December 2011, when Prince Philip was found to have a blocked coronary artery and underwent a "minimally invasive" procedure of coronary stenting.